Sudden stratospheric warming events (SSWs) are the most spectacular
atmospheric vertical coupling processes, well-known for being associated
with diverse wave activities in the upper atmosphere and ionosphere. The
first four solar tidal harmonics have been reported as being engaged.
Here, combining mesospheric winds detected by three mid-latitude radars,
we demonstrate at least the first six harmonics occur during SSW 2018.
Wavenumber diagnosis demonstrates that all six harmonics are dominated
by migrating components. Wavelet analyses reveal that the 4th, 5th, and
6th harmonics quench after the SSW onset. The six harmonics and the
quenching appear also in a statistical analysis based on near-12-year
observations from one of the radars. We attribute the quenching to
reversal of the background eastward wind.